1. Field of the Invention
The present invention relates to an ink drier for drying an ink on a paper after image formation and an ink jet type image forming apparatus mounting the ink drier, and more particularly, to an ink drier comprising a semicylindrical paper drying passageway for upward inverting a paper conveyed immediately after printing and a heat source provided on the central side of a circular arc of the semicylindrical paper drying passageway, and an ink jet type image forming apparatus mounting the ink drier.
2. Description of the Prior Art
In an ink jet type image forming apparatus, a time required for drying an ink after image formation considerably influences an efficiency of a whole printing process. In particular, a pigment based black ink capable of easily obtaining high picture quality generally requires a long time for drying. Therefore, in the case of an image having a high area ratio of a black dot such as a black solid, a long time is required for drying the ink, thereby deteriorating an increase in the speed of a printing operation. On the other hand, if the speed of the printing operation is increased carelessly, a conveying roller comes in contact with a print surface of a paper or the paper is mounted on a discharge tray in such a state that the ink is dried:incompletely, for example. Consequently, there is a drawback that the print surface or back face of the paper is stained with the ink.
For example, Japanese Patent Application Laid-Open Sho 63 No.252772 has proposed an ink jet type printer mounting an ink drier for drying a paper immediately after printing.
As shown in FIG. 1, a printer Z0 proposed in the above-mentioned publication comprises a paper tray 51 for storing a print paper, a pinch roller 52 for conveying the paper in the paper tray 51 one by one, an ink jet type print head 53 for forming an image on the paper conveyed by the pinch roller 52, a semicylindrical paper drying passageway 54 for upward inverting the paper on which an image is formed by the print head 53, an infrared heat source 55 provided in the vicinity of the center of a circular arc of the paper drying passageway 54, a reflecting plate 56 provided on the rear face side of the infrared heat source 55 with respect to the paper drying passageway 54, a discharge roller 57 for discharging the paper conveyed along the paper drying passageway 54, and a discharge tray 58 for accumulating the paper discharged through the discharge roller 57.
A series of printing processes in the printer Z0 will be briefly described below. First of all, one uppermost paper mounted in the paper tray 51 is taken out and is conveyed at a constant speed below the print head 53 through the pinch roller 52. In that case, the print head 53 forms an image on the paper while carrying out a scan in a direction orthogonal to a paper conveying direction. The paper sequentially enters the paper drying passageway 54 from a portion where an image is formed by the print head 53, and is conveyed along the semicylindrical paper dying passageway 54. At this time, an ink on the paper is dried with infrared rays directly irradiated from the infrared heat source 55 or infrared rays reflected by the reflecting plate 56 and indirectly irradiated. The paper having the ink dried which is conveyed along the paper drying passageway 54 is discharged onto the discharge tray 58 through the discharge roller 57.
The printer Z0 mounts an ink drier comprising the semicylindrical paper drying passageway 54, the heat source 55, the reflecting plate 56 and the like. Therefore, a black solid image formed by a lazy drying black ink can also be dried in a short time, for example. Thus, it is possible to increase the speed of a printing operation while maintaining high picture quality. Moreover, the paper is inverted upward and discharged along the semicylindrical paper drying passageway 54. Consequently, there are also advantages that the size of the device can be reduced and the paper can be mounted in correct order.
In the conventional printer Z0, however, only the pinch roller 52 and the discharge roller 57 are provided on the upstream and downstream sides of the paper drying passageway 54 as conveying means for conveying the paper along the paper drying passageway 54. Accordingly, the paper basically conforms to an internal surface with only the rigidity of the paper itself over the paper drying passageway 54. In the case of a paper having a small rigidity such as a thin sheet or a paper in a high humid state, accordingly, a tip thereof droops down by self weight during conveying over the paper drying passageway 54. Consequently, there is a fear that a paper jam might be caused and the paper might come in contact with the heat source 55, thereby catching fire in the worst case.
With the above-mentioned structure, furthermore, a paper having a smaller size than a path length between the pinch roller 52 and the discharge roller 57 cannot be used.
If such a paper is used by mistake, there is a fear that the paper jam might be caused or the paper might come in contact with the heat source 55, thereby catching fire in the same manner as in the case in which the paper having a small rigidity is used.
Moreover, the heat source is provided in the vicinity of the center of the circular arc of the semicylindrical paper conveying passageway. Therefore, heat is uniformly irradiated over the whole paper conveying passageway so that a constant time or more is required for drying an ink. For this reason, there is also a problem in that a drying path length is determined by the drying time and the size of the apparatus cannot be reduced.
In consideration of the above-mentioned circumstances, it is an object of the present invention to provide an ink drier capable of normally and safely drying an ink on a paper having a small rigidity or a paper having a small size without disadvantages such as a paper jam or an ignition caused by a contact with a heat source, and an ink jet type image forming apparatus mounting the ink drier.
In order to achieve the above-mentioned object, the present invention has the following aspects.
A first aspect of the present invention is directed to an ink drier comprising a semicylindrical paper drying passageway for upward inverting a paper conveyed immediately after printing, a heat source provided on a central side of a circular arc of the paper drying passageway, and paper holding means for continuously holding the paper along the paper drying passageway.
A second aspect of the present invention is directed to the ink drier according to the first aspect, wherein more heat energy sent from the heat source is irradiated onto a paper input side of the paper drying passageway than a paper output side thereof.
A third aspect of the present invention is directed to the ink drier according to the second aspect, wherein the heat source is provided closer to the paper input side than the center of the circular arc of the paper drying passageway.
A fourth aspect of the present invention is directed to the ink drier according to the second aspect, further comprising a reflecting plate provided on a rear face side of the heat source with respect to the paper drying passageway and serving to reflect more heat energy which is not used for paper drying but is dissipated toward the paper input side of the paper drying passageway than the paper output side thereof.
A fifth aspect of the present invention is directed to the ink drier according to the third aspect, further comprising a reflecting plate provided on a rear face side of the heat source with respect to the paper drying passageway and serving to reflect more heat energy which is not used for paper drying but is dissipated toward the paper input side of the paper drying passageway than the paper output side thereof.
A sixth aspect of the present invention is directed to the ink drier according to the first aspect, wherein the paper holding means utilizes air suction.
A seventh aspect of the present invention is directed to the ink drier according to the first aspect, wherein the paper holding means utilizes electrostatic attraction.
An eighth aspect of the present invention is directed to the ink drier according to the first aspect, further comprising paper conveying means for continuously conveying the paper along the paper drying passageway.
A ninth aspect of the present invention is directed to the ink drier according to the eighth aspect, wherein the paper conveying means is constituted by a plurality of rollers provided along the paper drying passageway.
A tenth aspect of the present invention is directed to the ink drier according to the ninth aspect, wherein the rollers are interlocked through one endless belt.
An eleventh aspect of the present invention is directed to the ink drier according to the eighth aspect, wherein the paper conveying means is constituted by a belt provided along the paper drying passageway.
A twelfth aspect of the present invention is directed to the ink drier according to the eleventh aspect, wherein the belt as the paper conveying means is guided by a guide member provided along edge portions on both sides of the paper drying passageway.
A thirteenth aspect of the present invention is directed to the ink drier according to the first aspect, wherein curl correcting means for correcting a curl of the paper is provided on a downstream side of the paper drying passageway.
A fourteenth aspect of the present invention is directed to the ink drier according to the thirteenth aspect, wherein the curl correcting means is constituted by rollers having different hardnesses which come in pressure-contact with each other.
A fifteenth aspect of the present invention is directed to the ink drier according to the fourteenth aspect, wherein the rollers having different hardnesses are constituted by elastic roller and rigid roller.
A sixteenth aspect of the present invention is directed to the ink drier according to the thirteenth aspect, wherein the curl correcting means is constituted by rollers having different diameters which come in pressure-contact with each other.
A seventeenth aspect of the present invention is directed to an ink jet type image forming apparatus mounting an ink drier comprising a semicylindrical paper drying passageway for upward inverting a paper conveyed immediately after printing, a heat source provided on a central side of a circular arc of the paper drying passageway, and paper holding means for continuously holding the paper along the paper drying passageway.
According to the present invention having the above-mentioned structure, when the paper is to be conveyed along the paper drying passageway immediately after printing, the paper is continuously held along the paper conveying passageway. Therefore, even in the case in which a paper having a small rigidity such as a thin sheet or a paper in a high humid state is used, for example, the tip of the paper does not droop down by self weight. Thus, it is possible to reliably prevent the drawback such as a paper jam or an ignition caused by a contact with a heat source.
If the paper holding means utilizes the air suction or the electrostatic attraction, for example, the paper can be held reliably with a simple mechanism.
The ink drier having the above-mentioned structure can be constituted such that more heat energy sent from the heat source is irradiated onto the paper input side of the paper drying passageway than the paper output side. Consequently, the heat source may be provided closer to the paper input side than the center of the circular arc of the paper drying passageway, or there may be disposed with a reflecting plate provided on the rear face side of the heat source with respect to the paper drying passageway and serving to reflect more heat energy which is not used for paper drying but is dissipated on the paper input side of the paper drying passageway than the paper output side thereof. The reflecting plate may adjust the direction of reflection of the heat energy depending on its angle and shape.
According to the above-mentioned structure, more heat energy is irradiated onto the paper input side of the paper drying passageway than the paper output side thereof. Therefore, a time required for drying can be shortened so that a paper conveying path length can be reduced and a small-sized structure can be obtained.
It is also possible to add, to the above-mentioned structure, the paper conveying means for continuously conveying the paper along the semicylindrical paper drying passageway. With such a structure, the paper is continuously conveyed along the paper drying passageway. Consequently, even in the case in which a paper having a smaller length than the path length of the paper drying passageway is used, for example, the paper can be conveyed reliably along the paper drying passageway without a stoppage during the conveying.
It can be proposed that the paper conveying means is constituted by a plurality of rollers provided along the paper drying passageway, for example. In this case, the rollers can be interlocked by one endless belt, for example.
Alternatively, the paper conveying means can also be constituted by a belt provided along the paper drying passageway. With such a structure, there also are advantages in that the mechanism can be more simplified and the air suction, the electrostatic attraction and other paper holding means can also be incorporated as well comparatively easily and the degree of freedom of the paper holding means can be increased.
The belt as the paper conveying means may be guided semicylindrically by the guide member provided along the edge portions on both sides of the paper drying passageway, for example.
Furthermore, if the curl correcting means for correcting the curl of the paper is provided on the downstream side of the paper drying passageway, the paper is discharged in such a state that an inward curl generated by the passage through the paper drying passageway is corrected. Therefore, it is possible to obtain more excellent results of printing.
If the curl correcting means is constituted by the rollers having different hardnesses for example, the elastic roller and the rigid roller, which come in pressure-contact with each other, reliable correction can be achieved with a simple structure. Moreover, even if the curl correcting means is constituted by the rollers having different diameters which come in pressure-contact with each other, the same effects can be obtained.
The ink drier having the above-mentioned structure can be incorporated in an ink jet type image forming apparatus such as a printer or a facsimile, and furthermore, may be a separate device which can be provided externally.